yo H,
First off.I've tried to enter this Reply 4 times so far; I keep getting this error message; "You are not allowed to use that image extension on this board.." However, I don't know which image this is ref. to!
So I'll have to go thru it again and delete all image ext. and just post the URL for the image.
Your Speedo/Odometer is called the Programmable Speedometer Odometer Module (PSOM)
You can Calibrate it; due to tire size change where a larger diameter tire will show what you have, faster indication than actual speed (and gearing doesn't matter for a PSOM to be accurate)
Recalibrate Electronic Speedo:
To adjust the Speedometer and odometer on the late model Bronco. (Note: The module can only be reprogrammed six times.) But there is a device out there to recal it such as the Superlift® TruSpeed™ Speed Sensor Recalibrator;
Overview & Installation Instructions in 92-96
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By Benjamin Ratterree
1. Check whether the conversion constant in the speedometer is correct with the following procedure:
Press and hold the RESET button on the front of the speedometer while turning the key to RUN.
Release the RESET button. The pointer will prove out and some codes will appear on the odometer display. If an "E" is on the left side of the display, the module is programmed for English display mode and should have English graphics (mph). A lower case "o" signifies an overseas (metric) graphics (kph). Verify the graphics and display modes agree. (The number appearing after the type is the microprocessor revision level and is not used in this test.)
Rress and release the RESET button again. The conversion constant and the word CAL will be shown on the odometer display.
Check the conversion constant shown on the odometer display with the chart below and verify the correct constant is entered.
Turn off the key to exit this test.
2. Reprogram speed conversion constant using the following procedure:
Locate the dealer mode programming enable single-terminal connector. The connector is located at the bottom of the instrument panel below the center of the glove box. On all vehicles, the dealer mode enable wire is Circuit #567 (LB/Y).
- here is the PSOM connector from under the dash, notice the flat pin in the connector,
pic by jslax
Insert metal clip in service wire panel connector. Clip other end to vehicle ground while the key is in the OFF position.
Turn key to RUN (not crank) position while holding down the trip odometer RESET button on speedometer. Release RESET button.
Speedometer will prove out (sweep across dial and back). The English/Metric and revision levels will be displayed. The last number of the display is the dealer mode programming lockout count. This count shows the number of allowable conversion constant changes remaining. When the count is zero (0), no additional changes can be made to this instrument cluster. If a conversion constant change is required, a service instrument cluster must be ordered. Refer to this section for ordering information.
Press and release RESET button again and PSOM conversion constant (without the decimal point) followed by the word CAL.
Press and release the odometer SELECT button as many times as necessary to change conversion constant to the correct value.
NOTE: Pressing and releasing the RESET button to lock in the new Conversion Constant reduces the number of times the PSOM can be reprogrammed by one count. The module can only be reprogrammed six times. If you change your mind and want to go back to the old conversion constant, turn the ignition switch off before you lock in the new constant.
When the correct new value is displayed in odometer window, press and release the RESET button to lock in the new conversion constant.
Turn the key off and remove the ground wire. Verify proper speedometer operation.
To find conversion constants for tires with 15 inch rims that are not listed in chart, above multiply the revolutions per mile (at 45mph) of your tire times .0135. For 16 inch rims multiply by .015. The revs/mile can be found at your tire manufacturers web site. There are slight variations in revs/mile per tire manufacturers, but using one like the popular BFG A/T (see below) will get you very close.
Example: BFG AT 33x12.50R15LT/C
Revs/mile= 636
636 rev/mile X .0135 = 8.59
8.59 would be your conversion constant
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Here is a listing of popular oversize BFG All-Terrain tires with conversion constants:
Tire Size Revs/mile (at 45mph) Conversion Constant
30x9.50R15LT/C 705 9.52
31x10.50R15LT/C 677 9.14
32x11.50R15LT/C 656 8.86
33x12.50R15LT/C 636 8.59
35x12.50R15LT/C 599 8.09 "
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"...First, you'll need to know the actual height of the tires, not the nominal height of 35" that's printed on the sidewall. To get that, make a mark on the edge of the tire at the ground, and mark the ground directly under the mark. Now, roll the truck far enough for the tire to have made three revolutions. When your mark on the tire is at the very bottom, near the ground, mark the ground again, and measure the distance between the two marks on the ground. Divide that distance by three, since there were three revolutions of the tire, then divide that number, (which is the circumference of your tire,) by 3.14. The answer you have is the true height of your tire. Write that number
down, because you'll need it for the next step. Divide 30282 by your actual height. If your true height is 34", the math goes something like this: 30282/34=891. That would be your speedometer calibration code."
by Rodney
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PSOM Calculator at ArkansasMud.com
The following form can be used to find your PSOM conversion constant
by feeding it your true, unloaded tire diameter. A 35" BFG MT KM is only
34.8" tall, and most other tires are shorter than the listed diameters as well.
I make no accuracy guarantees but these seem to be very close to the
few published FORD values that I've seen. Visit National Tire and go to
"SPECS" to find your tire's actual diameter. This only works for 92-96 Broncos
and F150 trucks, though to extend it to 92-97 F250/350 trucks with the Sterling 10.25"
rear axle just multiply your constant by the fraction (120/108). Keep in mind that these
values are for a new tire with full tread, and that if you start with full tread Boggers and
run them down to the belts, you're talking about losing several inches of diameter!
Click here for PSOM programming procedure. Keep em muddy!
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Go here for the Constant Calculator (92-96)
Source: by Muddybronco (Eric) at
http://web.archive.org/web/20070324124950/http://www.arkansasmud.com/psomcalc.html
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& Conversion Constants TSB 94-16-16 for 92-94 Bronco, F Series, F 47, Aerostar, Econoline
Source: by Ford via Steve83
http://www.thedieselstop.com/faq/9497faq/maint/stj/images/k17295c.gif
LEGEND
http://www.thedieselstop.com/faq/9497faq/maint/stj/stji1015.htm
27 — PSOM Test Circuit (Part of 14401)
from 1996 F-150, F-250, F-350, F-Super Duty Chassis Cab, Motorhome Chassis, and Bronco Workshop Manual
